Bottom hole hydraulic pump



Dec. 31, 1957 c. H. KANGAs BOTTOM HOLE HYDRAULIC PUMP 2 Sheets--Sheei'I 1 Filed March 14, 1956 Dec. 31, 1957 c. H. KANGAS BOTTOM HOLE HYDRAULIC PUMP 2A Sheets-Sheet 2 Filed March 14, 1956 INVENTOR. C. H. KANGAS JwuSQ-w i xi AT TORN EYS United States Patent O` BOTTOM HOLE HYDRAULIC PUMP Charles H. Kangas, Taft, Calif., assignor to Phillips Petroleum Company, a corporation of Delaware Application March 14, 1956, Serial No. 571,490

Claims. (Cl. 103-4) This invention relates to a bottom hole hydraulic pump. In one aspect it relates to a bottom hole hydraulic pump for use in dual zone producing wells. In another aspect it relates to a single zone double acting hydraulic pump. In a still further aspect it relates to a free-type hydraulic pump particularly useful in connection with deep Well pumping operations.

Oil wells often intersect several independent strata from which oil may be produced. In pumping Wells of this nature, it is often desirable or necessary that the oil produced from the separate zones be removed as independent streams. This can be accomplished either by employing a plurality of pumps in different bore holes in the same field or by separating the inlets of a plurality of pumps in a single bore hole in such a manner that the oil in the two zones is removed through separate conduits. Various types of dual zone deep well pump assemblies are known in the art for pumping such wells. However, the known pumping structures have not been entirely satisfactory because of the relative complexity of the devices. It is desired that the pump structure be of such configuration that it can readily be removed from the Well for servicing operations without removing the entire well tubing and hydraulic liuid lines. Furthermore, it is desired that the pump structure be relatively simple and employ a minimum number of moving parts. Another desirable feature is that such a pumping structure is readily convertible from dual Zone to single zone producing operations.

In my copending application Serial No. 462,478, filed October l5, 1954, I have disclosed and claimed a bottom hole hydraulic pump which is characterized by the abovementioned desirable features. However, the hydraulic pump set forth there is particularly suited in connection with the production of relatively shallow rather than deep wells. The hydraulic pump of the instant invention is particularly suited in connection with deep well pumping operations and in some aspects is related to the hydraulic pump of the aforementioned application.

Accordingly, it is an object of this invention to provide a hydraulic pump adapted to remove fluid simultaneously from two spaced well formations without mixing the pumped fluids.

Another object is to provide a deep well hydraulic pump system in which the pump is so adapted that the ratio of hydraulic or power fluid t-o the formation or produced fluid is always greater than l.

Another object is to provide a bottom hole hydraulic pump characterized by novel valve actuation means to prevent the pump from sticking on dead center.

A further object is to provide a bottom hole hydraulic pump for use in pumping operations of either single or dual zone producing wells.

A still further object is to provide a deep well hydraulic pump of such configuration that it can be readily removed from the well without removing the entire well tubing and hydraulic iiuid supply lines.

Other objects, advantages, and features of this invenl tion will become apparent to those skilled in the artv from the following detailed description taken in conjunction with the accompanying drawing in which:

Figure 1 is an elevation view, shown partly in section, of a dual zone producing well having the pumping structure of this invention inserted therein;

Figure 2 is a vertical schematic view of the hydraulic pump of this invention;

Figure 3 is a vertical isometric view, in quarter-section, of the removable pump assembly of this invention;

Figure 4 is a Vertical isometric view, in quarter-section, of the housing in which the pump assembly of Figure 3 is inserted; and

Figure 5 is a schematic view of a portion of Figure 2, whereby the pump of the other figures can be modified for use in a single zone producing well.

Referring now to the drawings, and to Figure 1 in.

casing string 11 between the two formations. Packer 18 is provided with a central opening 19, Figure 2, which can be closed by a hinged check valve 21, if desired. After packer 18 is set in the casing string 11, a pump assembly housing 22 is lowered into the well on the lower end of a tubing string 23. A second packer 24 is carried by tubing string 23 above pump assembly housing 22 and above formation 14.

With reference to Figure 2, the lower end of the tubing string is attached to a cylinder barrel 26 by means of a collar 27, shown more clearly in Figure 4. Disposed in the upper portion of the pump assembly housing 22 is an upper valve assembly or plug generally designated 28 of the pumping unit having a first slide valve 29 positioned in a central bore 31 therein. A fiuid passage 32 communicates at one end with bore 31 and at the other end with a hydraulic fiuid supplying conduit 33 which extends upwardly through casing head 17, Figure 1, to the surface of the well. A fluid passage 34 communicates at one end with bore 31 and at the other end with a first hydraulic fiuid chamber 36 which is defined in part by the upper inner wall of cylinder barrel 26 and the lower end of valve assembly 28 from which depends a conduit 37. The region 38 above the valve assembly 28 communicates with conduit 37 through the valve assembly 28 by reason of fluid passage 39 having a check valve 41 therein to prevent ow of fluid from region 38 into conduit 37. A fluid passage 42 provided with check valves 43 and 44 permits fluid dow from formation 14 into conduit 37 but prevents flow in the reverse direction.

Cylinder barrel 26 terminates at its lower end in a lower valve assembly or plug generally designated 46 having a second slide valve 47 positioned in a central bore 48 therein. A fiuid passage 49 communicates at one end with bore 48 and at the other end with the lower end of the hydraulic fluid supplying conduit 33 which exteriorly extends down the length of the pumping assembly housing 22. Fluid passage 51 communicates at one end with bore 48 and at the other end with a second hydraulic fluid chamber 52 which is defined in part by the lower inner wall of cylinder barrel 26 and the upper end of valve assembly 46 from which upwardly extends a conduit 53. The lower end of housing 22 forms an elongated conduit 54 which extends through the central opening 19 in packer 18 by displacing valve 21 downwardly. The lower end of conduit 54 is provided with a check valve 56 which permits the flow of oil from vformation 16 into the interior of conduit 54 but prevents Patented Dec. 31, 1957- flow in the reverse direction. Communication between conduit 54 and conduit 53 ishad by reason of fluid passage 57 provided with check valve 58 to prevent flow from passage 57 into conduit 54. Conduit 53 also communicates at its lower end with uid passage 59 whichY communicates in turn with conduit 60 which exteriorly extends along the outside of housing 22 and opens into region 61 at its upper end. Passage 59 is provided' with a check valve 65 to prevent fluid from owing back into conduit 53 from conduit 60.

A hollow elongated piston generally designated 62 is slidably disposed within cylinder barrel 26 and is provided with an upper pumping member 63 provided with opening 64 and a lower pumping member 66 provided with opening 67. Conduits 37 and 53 pass through openings 64 and 67 respectively and are secured at the lower and upper ends respectively to a central valve actuating assembly generally designated 68 which comprises a housing 69 in slidable engagement with the inner wall of piston 62. Conduits 37 and 53 are provided with openings 71 and 72 respectively adjacent housing 69 so as to permit communication with formation liquid chambers 73 and 74 respectively which are defined in turn by the inner wall of piston 62 and housing 69. Slide valves 29 and 47 are secured to valve actuating rods 76 and 77 respectively which extend through conduits 37 and 53 respectively and pass through openings into housing 69 wherein they are secured to links 78 and 79 respectively. The latter members are in turn secured to a pivotable member 81 which is pivotally connected to the inside of housing 69 by means of bracket 82 and pin 83. Member 81 has a tapered end portion 84 adapted to bear against a roller 86 supported by a spring 87. A slidable member generally designated 88 comprises a spring retainer 89 and two pins 90 and 91 which extend through housing 69 into chambers 73 and 74 respectively.

Slide valves 29 and 47 are provided with pressure equalizing passages 92, 93 and annular iluid passages 94, 95 respectively. The upper valve assembly 28 is provided with a hydraulic tluid exhaust passage 97 which communicates at one end with bore 31 and at the other end with passage 39. Lower valve` assembly 46 is also provided with a hydraulic uid exhaust passage 98 which communicates at one end with bore 48 and at the other end with a fluid passage 99 which in turn communicates at one end with` passage 59. At its` other end, passageway 99 communicates with an annular recess 101. The lower end of housing 22 is provided with a plunger 102 which is forced into recess 101` by a compression spring 103 to lock the pump assembly of Figure 3 in the barrel 26 of the housing of Figure 4.

A compression spring, not shown, can be disposed between conduit 53 and the lower valve assembly 46, similar to the manner shown in the pump of the aforementioned application, to provide a flexible attachment between 53 and 46 to prevent compression forces being exerted on conduit 53.

The manner in which the hydraulic pump of the present invention is placed in position in a well will now be described and reference will be made to the several figures.

Tubing string 23 is lowered into the well and positioned. with housing 22 forming a seal with packer 18 and with expandable packer 24 set toseal the region between housing 22 and casing string 11. The pump assembly illustrated in Figure 3 is then positioned in the tubing string 23. at the surface of the well. Casing head 17, Figure l, is attached to the casing string 11 such that a conduit 104 having a valve `105 therein communicates with the top of tubing string 23. An oil reservoir 106 is connectedto the. inlet' port of a hydraulic pump 107 by a` conduit 108. Conduit 33 extends out of casing head` 17 at: the surface and communicates through' a valve=109 to the outlet of pump 107. Conduits 33`a1:1 dA 104lare connectedby a conduit 111 having a valve 112` therein. Conduit 113 having a valve 114 therein connects casing head 17 with conduit 33. Conduits 116 and 117, hav-ing respective valves 118 and 119 therein, also communicate with oil reservoir 106. The second end of conduit 116 is connected to a conduit 121 which communicates at one end with the interior of casing head 17 and at the other end with a valve 122 in a conduit 123. After the pump assembly of Figure 3 is positioned within tubing string 23, valves 105, 109 and 114 are closed and valve 112 is opened so that pump 107 forces hydraulic fluid from reservoir 106 into the top of tubing string 23. This forces the pump assembly of Figure 3 downwardly through tubing string 23 until it seats in the pump assembly housing of Figure 4, which is attached to the lower end of tubing string 23, as illustrated in Figure 2.

When the pump assembly is located in position within barrel 26valve 112 is closed and valves 105 and 109 are opened, see Figure 1. Hydraulic fluid from reservoir 106 is then directed by pump 107 through conduit 33 and then into the pumping assembly of this invention by means of either passage 32 or passage 49, Figure 2, depending on the position of the slide valves 29, 47. With the slide valves 29, 47 in the positions indicated in Figure 2, hydraulic fluid from conduit 33 will be supplied to passage 49 of the lower valve assembly 46. The hydraulic fluid then ows from annular passage 95 through passage 51 and into hydraulic fluid chamber 52 where it exerts a force on lower pump member 66 causing the piston to slidably move upward within barrel 26. Near the rtop of the upstroke of the piston 62, the lower pump member 66 contacts slidable pin 91, forcing it upward. This in turn causes slidable member 88 in general to move upward and roller 86 moves toward the pointed end of the tapered end portion 84 of pivoted member 81. At the top of the upstroke, roller 86 passes the pointed end and pivoted member 81 is quickly moved counterclockwise. As a result of the quick movement of pivoted member 81, the valve actuating rods 76 and 77 are both pulled downward along with the sliding valves 29 and 47. The upstroke of the piston 62 is now completed and the downstroke is about to begin. At this point, it is to be noted that hydraulic fluid in conduit 33 will no longer be supplied to passage 49 because the annular recess 95 no longer communicates therewith. Rather, hydraulic uid from conduit 33 can now be supplied to the passage 32 of theupper valve assembly 28 because the annular recess 94 and passage 34 will now be in communication therewith. Hydraulic uid will now enter hydraulic fluid chamber 36 through passage 34. The pressure of the hydraulic uid in chamber 34 is exerted on upper pump member 63 causing the piston 62 to move downward within barrel 26. Piston 62 is forced downward until the upper pump member 63 contacts the upper end of pin of the slidable member 88 near the bottom of the downstroke. Pin 90 is forced downward into housing 69 until at the bottom of the downstroke the roller 86 passes the point of pivoted member 81 causing the latter to quicklymove clockwise. As a result of this move ment, the valve actuating rods 76 and 77 are forced upward causing the slidingva'lves to return to their original positions as shown in Figure 2.

During the upstroke of piston 62, as described above, liquid from formation 16 which was supplied on the downstroke to chamber 74 through conduit 54, passage 57, conduit 53 and opening 72 will be exhausted from chamber 7.4 through opening 72, conduit 53, passage 59, and conduit 60 into the region 61 (the annular space between the tubing string 23 and the casing string 11) in which it rises to the surface where it is removed through conduit 121. At the same time, any hydraulic fluid remaining in. chamber 36 is exhausted through passage 34, annular. recess 94, passages 97 and 39 into the region 38, that is the interior of tubing string 23, in which it rises `to the surface where it is removed through conduit 104.

aiaoas.

I While both hydraulic iiuid from chamber 36 and formation liquid from chamber 74 are thus being exhausted on the upstroke, liquid from formation 14enters the upper valve housing 28 through passage 42, into conduit 37, through opening 71, and into chamber 73.

During the downstroke of piston 62, liquid from formation 14 which was supplied on the upstroke to chamber 73 through passages 42, 39, conduit 37 and opening 71 will be exhausted from chamber 73 through opening 71, conduit `37, and passage 39 into the region 28 in tubing string 23 in which it rises to the surface (as did hydraulic iiuid` from chamber 36 on the upstroke). At the same time, any hydraulic fluid remaining in chamber 52 is exhausted through passage 51, annular recess 95, pas-sages 98, 99, 59 and conduit 60 into region 61 in which it rises to the surface (as did formation fluid from chamber 74 on the upstroke).

It is apparent that though the hydraulic iiuid is mixed, after it is exhaused, with the liquid from the two independent formations, the liquids from the latter are never mixedbecause the liquid from the upper formation 14 is conveyed to the surface by the tubing string 23 and the liquid from the lower formation 16 is conveyed to the surface in the annular space 61 between the casing 11 and the tubing string 23. In this manner, the production from two spaced formations is accomplished without admixing the pumped fluids.

Because the pressure of the hydraulic fluid is appliedr to the larger sides of the pump members 63 and 66, the ratio of hydraulic or power uid to formation or produced fluid is always greater than 1, thus making the operation of the pump of this invention particularly suitable in relatively deep wells.

When it is desired to remove the pumping assembly from cylinder barrel 26, hydraulic uid is forced by pump 107 through line 113 into region 61, the annular space between tubing 23 and casing 11, by opening valve 114 and closing valves 109 and 111. This fluid is directed through conduit 60 and passage 99 to annular recess 101. The fluid pressure in this region displaces plunger 102 against the force of spring 103 to disengage the pumping assembly from the cylinder 26. The fluid pressure in region 101 also exerts an upward force on the pump assembly which forces it upwardly through the tubing string 23. The pump assembly can thus be readily removed without disturbing the tubing string or the fluid supply conduit 33. Check valve 44 serves to prevent the exit of this hydraulic fluid from the cylinder 26.

The outer ends of passages 32 and 59 terminate in annular recesses to provide communication with the adjacent passages 33 and 60 respectively.

The upper valve assembly 2S is provided with a spear head or latching member 131 projecting from its upper end into the region 38, to receive a pulling tool toen- .able the pump assembly to be pulled out of the well if necessary.

When it is desired to employ the pumping apparatus of this invention in a single zone producing well, if it is desired to produce all the iiuid through tubing 23, the upper portion of the pumping assembly is modified, for example, as shown in Figure 5. Referring now to that figure, conduit 60 is similar to conduit 60 of Figure 2 except that it communicates with tubing string 23'kabove packer 24 by reason of conduit 126. A plug 127 is slidably mounted in conduit 60 and is normallyldisposed in conduit 60 so as to allow communication between the latter and conduit 126 and to prevent communication of the lower portion of conduit 60' with that upper portion of conduit 60 which communicates at its upper end with annulus 61. Plug 127 is retained in this normal position by means of compression spring 12S which abuts at its lower end conduit 126 and abuts at its upper end plug 127.` Liquid pumped up conduit 60 on the upstroke is conveyed to tubing string 23 via conduit 126, plug 127 being retained'above the opening 129 be- 6 tween conduits 60' and 126 by spring 128. Thus, liquid in conduit 60' is conveyed `to the surface in tubing string 23 instead of the annulus 61 as was the case with the pumping operation of a dual zone well as described hereinbefore.

Removal of the pumping assembly may still be accomplished by pumping hydraulic uid via conduit 113, annulus 61 and conduit 60', as hereinbefore described, since the pumped hydraulic iiuid in the annulus 61 will cause the plug 127 to move downward against the force of spring 128 thereby preventing communication between conduit 60 and conduit 126. The plug 127 will thus move below the opening 129 permitting the pumped hydraulic fluid to enter from the annulus into the lower portion of conduit 60'.

In producing a single zone well with the hydraulic pump of this invention, packer 18 is not needed because the liquid from the single zone is permitted to enter the pump .assembly through both check valves 44 and 56. The operation of the pump is substantially the same as previously described except all of the liquid is removed from a common zone.

While it is preferred to employ the modification of Figure 5 when producing a 4single zone Well, it should be understood that I do not intend to so limit my invention since it sometimes is desirable to produce a single Zone by conveying the produced liquid to the surface in two streams, e. g., via tubing string 23 and annulus 61.

Various modifications of this invention will become apparent to those skilled in the art without departing from the scope thereof and it should be understood that while the invention, has been described in conjunction with a present preferred embodiment, it should be apparent that the invention is not limited thereto.

I claim:

1. A double action pump comprising, in combination, a housing defining a piston chamber, first and second inlets at each end of said housing, check valve means in each of said second inlets to prevent flow of fluid from the interior of said housing to the exterior thereof, an outlet at each end of said housing, check valve means in each of said outlets to prevent ilow of fluid from the exterior of said housing to the interior thereof, hydraulic fluid conduit means communicating between a region exterior of said housing and said first inlets, exhaust fluid conduit means communicating between a region exterior of said housing and said outlets, a hollow reciprocating piston in said piston chamber and dividing the same into a pair of hydraulic fluid chambers, a pair of valve means, one at each end of said housing, for alternately supplying and exhausing hydraulic uid to and from said hydraulic uid chambers through said first inlets and said outlets respectively, one of said valve means being adapted in a first position to supply one of said hydraulic fluid chambers when the other said valve means in a second position is exhausting the other hydraulic fluid chamber, means dividing said hollow piston into a pair of production uid chambers, first and second conduit means one end of each communicating with one of said outlets and the other end of each communicating with one of said production fluid chambers, a snap-action mechanism, connection means connected to each of said valve means and to said mechanism whereby activation of the latter causes said connection means to move one of said valve means to said first position and the other said valve means to said second position, and means adapted to actuate said mechanism upon the completion of the upstroke and downstroke of said piston.

2. A double action pump comprising, in combination, a housing defining a piston chamber, first and second inlets at each end of said housing, check valve means in each of said secondv inlets to prevent iiow of fluid from the' interior vof said housing to the exterior thereof, an outlet at each end of said housing, check valve means in each of said outlets to prevent flow of iiuid from the exterior of said housing to the interior thereof, hydraulic fluid conduit means communicating between a re gion exterior of said housing and said first inlets, exhaust fluid conduit means communicating between a region exterior of said housing and said outlets, a hollow reciprocating piston slidably disposed in said piston chamber and dividing the same into first and second hydraulic fluid chambers, a pair of sliding valves, one at each end of said housing, adapted to slidably move and direct hydraulic fluid from said first inlets into said first and second hydraulic fluid chambers alternatively, one of said fluid chambers not receiving hydraulic fluid being exhausted to one of said outlets through one of said valves, means dividing said hollow piston into first and second production fluid chambers, first and second conduit means passing through the upper and lower ends of said piston respectively and communicating at one end with said first and second productionifluid chambers respectively, the other ends communicating with said outlets, a snapaction mechanism disposed within said piston, a pair of rods axially disposed within said first and second conduit means and connected at one end with said valves and at the other end to said mechanism, said rods being adapted to slidably move said valves upon actuation of said mechanism, and means within said piston adapted to actuate said mechanism when contacted by said piston upon completion of the upstroke and downstroke of said piston.

3. A double action well pumping unit comprising, in combination, an elongated housing defining a piston chamber, said housing being adapted to be positioned in a well on the end of a tubing, an upper and lower plug disposed is respective endsof said housing, first and second inlets in each of said plugs, check valve means in each of said second inlets to prevent flow of fluid from the interior of said housing to the exterior thereof, an outlet in each of said plugs, check valve means in eachof said outlets to prevent flow of fiuid from the exterior of said housing to the interior thereof, said first inlets being connected to a hydraulic fluid tubing, each of said outlets being connected to a production fluid tubing, a hallow reciprocating piston slidably disposed in said piston chamber and dividing the same into first and second hydraulic fluid charnbers, a pair of sliding valves, one of each in said plugs, adapted to direct hydraulic fluid from said first inlets into said first and second hydraulic fluid chambers alternately, one of said hydraulic fluid chambers not reeciving hydraulic fluid being exhausted to` said production fluid tubing through one of said valves, means dividing said piston into first and second production fluid chambers, first and second conduit means passingl through the upper and lower ends of said piston respectively, one end of said conduit means communicating with one of said production fluid chambers, the other end communicating with one of said outlets, a snap-action mechanism within said piston, a pair `of rods each axially disposed within said conduit means and connected at one end ton one of said valves and operatively connected at the other end with said mechanism, said rods being adapted to move said valves upon actuation of said` mechanism, and a movable member connected to said mechanism and projecting `into said` hydraulic fluid' chambers whereby said piston contactsthe same upon the complction of its upstrolze and downstroke of the same thereby actuating said mechanism.

4. A double action well pumping unit comprising, in combination, an elongated housing defining a piston chamber, said housing being adapted to be positioned in a first wcll on the end of a tubing, an upper and lower plug disposed iu respective ends of said housing, first and second inlets in each of saidl plugs, check valve means in each of said second inlets to prevent flow of fluid from the interior of said housing to the exterior thereof, an outlet in each of said plugs, check valve means in` each of said outlets to prevent flow of uid from the exterior of said housing tothe interior thereof, said first inlets being connected to a hydraulic fluid tubing, each of said outlets being connected to a production fluid tubing, ay hollow reciprocating piston slidably disposed in said piston chamber and dividing the same into first and second hydraulic fluid chambers, said piston having upper and lower pumping members the outside crosssectional areas of which are larger than their inside cross-sectionalv areas, said pumping members having axial: openings therein, a pair of sliding valves, one of each in said plugs, adapted to direct hydraulic fluid from said first inlets` through first plug passages into said first and second hydraulic fluid chambers alternately. one of said hydraulic fluid chambers not receiving hydraulic fluid: being exhausted through a second plug passage which which communicates with said production tubing, means dividing said piston into first and second production fluid chambers, firstr and second conduit means slidably passing through said openings of said pumping members and secured to said plugs, first ends of said conduit means communicating with said outlets through a third plug passage and second ends of said conduit means communicating with said hydraulic fluid chambers, a snap-action mechanism within said piston, a pair of rods each of which are axially disposed in one of said conduit means and connected at one end to one of saidy valves and operatively connected at their other end to said mechanism, said rods being adapted to move said valves upon actuation of said mechanism, and a movable member operatively contacting said mechanism, said movable member having extremities which project into said hydraulic fluid chambers whereby said pumping members of said piston contacts the same alternately upon the completion of the upstroke and downstroke of said piston thereby causing said movable member to actuate saidy mechanism.

5. The apparatus of claim 4 further comprising a releasable locking mechanism adapted to lock one of said plugs to said housing.

6. The apparatus of claim 4 wherein said first tubing comprises said production tubing and wherein communication with the same and said outlet in said lower plug is had by a production fiuid conduit having a valve means associated therewith to normally allow said communication.

7. The combination in accordance with claim 4 further comprising a source of hydraulic fluid under pressure at the surface of the well, valved conduit means communicating with said source and said hydraulic fluid tubing, valved conduit means communicating with said source and said production tubing, and valved conduit means communicating with said source and said first tubing.

8. The combination in accordance with claim 4 further comprising a well packer extending outwardly from said housing at a region between said second inlets to engage the wall of the well.

9. The combination in accordance with claim 8 further comprising a second well packer extending outwardlyY from said housing at a region above said second inlet in said upper plug to engage the wall of the well.

l0. A double action well pumping unit comprising, in combination, an elongated cylindrical housing definingA a piston chamber, said housing being adapted to be positioned in a well on the end of a tubing, upper and lower cylindrical plugs slidably disposed in respective ends of said housing, first and second inlets in each of said plugs` axial bores in each of said plugs, a slidable valvein each of said bores, each of said valves having an annular recess, a hollow cylindrical piston slidably disposed in said piston chamber and dividing the same into first and secondliydraulic fluid chambers, said piston having upper and lower pumping members the outside-cross-sectional areas of which are larger than their inside cross-sectional areas, said pumping members having axial openings therein, first plug passages each communicating between one of said first inlets and one of said hydraulic uid chambers through one of said annular recesses when one of said sliding valves is in a rst position, a first outlet in said upper plug opening to said tubing, a second outlet in the wall of said lower plug opening to a production tubing, second plug passages each communicating between one of said hydraulic iluid chambers and one of said outlets through one of said annular recesses when one of said sliding valves is in a second position, said sliding valves each adapted in a first position to direct hydraulic fluid from one of said first inlets into the corresponding hydraulic fluid chamber, the hydraulic uid chamber not receiving hydraulic fluid being exhausted through one of said outlets when one of said valves is in a second position, means dividing said piston into first and second production fluid chambers, rst and second conduit means slidably passing through said openings of said pumping members and secured to said plugs, third plug passages each communicating with one of said second inlets and trst ends of one of said conduit means through said second plug passages, each of said production uid chambers communicating with one of said outlets through a second end of one of said conduit means, check valve means in said second plug passage to prevent ow of uid from the extension of said housing to the interior thereof, check valve means in said third plug passage to prevent ow of uid from the interior of said housing to the exterior thereof, a -snap-action mechanism within said piston, a pair of rods each of which is axially disposed in one of said conduit means and connected at one end to one of said valves and operatively connected at their other end to said mechanism, said rods being adapted to move said valves upon actuation of said mechanism, and a movable member operatively contacting said mechanism, said movable member having extremities which project into said hydraulic fluid chambers whereby said pumping members of said piston contacts the same alternately upon the completion of the upstroke and downstroke of said piston thereby causing said movable member to actuate said mechanism.

References Cited in the le of this patent UNITED STATES PATENTS 2,499,849 Coberly Mar. 7, 1950 2,605,712 Davis et al Aug. 5, 1952 2,625,882 Davis et al Jan. 20, 1953 U. Sv. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 2,818,022 December 31, 1957 Charles H. Kengas It s hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

(3011111111 '5, line 319 for greater than 1H read greater than one- @011mm 6', line 32, after Y"irwention" strike out the comme; line 51, for ""e'xhausing" read wexhaustingm; column '7, line 33, for "isrespeetive" read in respective-m; line 41, for "hallow" read wholloww; line 69, strike out "first" 'andnsert the same after "of a", same line; Column 8, line 16, strike out ."whieh", second occurrence; column 10, line 13, for "Contactsn read' umcontaetmm Signed. and sealed this 22nd day of April 1958o (SEAL) Attest:

KARL Ho AXLINE l ROBERT C. WATSON Attes'ting Officer Corrmissioner of Patents 

